I suggest you should stop that masturbation not because its dangerous or life threatening, its just not uncomfortable you know. Being a person who did it same during my teens, I know how strenuous it can be. Masturbating with your hands-on is the most comfortable way, as far as I'm concerned. May be you should try it.
See, your masturbation method has got nothing to do with your problems in sex. Its all bout the timing and your mindset when you have it. First of all, get rid of all these thoughts outta ur head. Talk it out, set a time or wait for it, and try it out with your partner. You should do fine.
I know you know this, but, play safe. Use Condoms.
Cheers
well u should cut down, thts one. and i do the mattress thing too but only when im lazy. lol. have time in between masterbation, a good time is a day or two. start off slow and work ur way up my friend. :) soon u will be ejaculating during sex. :)